Synchrotron Lights for Nano-Chemistry

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Modern synchrotrons, such as SOLEIL (near Paris), propose under the same roof several beamlines that operates with all types of lights, from hard to soft X-ray, from infra-red to UV. These are as many different ways to scrutinize the nano-matter and get a fuller picture of the mechanism of formation or evolution that are at play in any environment (wet, hot, liquid, with reactive gas...).

Of the nanoparticles that we are preparing each day in the lab, we know little. Surface state, inner-structure, presence of a ligand shell... all of those are investigated with routine characterization methods on a daily basis, but often require a more thorough investigation. Moreover, the synchrotron beamlines nowadays allow using a variety of sample environments (liquids, films, solids under gas flow, etc.), which simulate the conditions of use of the nanoparticles, eg. in a catalytic process. Our input is two-fold: first, demonstrate the feasability and exploit the results of in situ monitoring on complex samples of nanoparticles, and second, act as a driving force for the development of new in situ cells (eg. for FTIR spectroscopy) that fit the requirements of our fellow chemists.

At SOLEIL, we are particularly working on TEMPO (soft x-rays), LUCIA (tender x-rays), SAMBA (hard x-rays), SMIS (infrared light).

Related papers:

Guidelines for the Molybdenum Oxidation State and Geometry from X-ray Absorption Spectroscopy at the Mo L2,3 -Edges

X-ray absorption near-edge structure (XANES) is a particularly well-adapted technique to study the L2,3-edges of Mo (2520–2625 eV). It provides information on both the electronic and local structures of metal-containing species and allows drawing structure–activity relationships. However, L2,3-edges are difficult to interpret, especially for 4d and 5d transition metals. In this work, we provide a method for their interpretation based on a library of spectra of simple Mo compounds. We suggest using the L3-edge to determine the oxidation state and the L2-edge to gain insight on the geometry around Mo atoms. This method is then applied to a series of molybdenum sulfide compounds to rationalize their structures.

JPCC2021

A.P. Freitas, R. F. André, C. Poucin, T. K.-C. Le, J. Imbao, B. Lassalle-Kaiser, S. Carenco. Guidelines for the Molybdenum Oxidation State and Geometry from X-Ray Absorption Spectroscopy at the Mo L2,3-Edges. J. Phys. Chem. C 2021, 10.1021/acs.jpcc.1c01875.

Different reactivity of rutile and anatase TiO2 nanoparticles: synthesis and surface states of nanoparticles of mixed-valence Magnéli oxides

Understanding the surface reactivity of titanium oxides Magnéli phases that contain both Ti(IV) and Ti(III) is of prime importance. This article describes a new synthetic route to 50 nm carbon-free Ti4O7 and Ti6O11 nanoparticles.The surface reactivity of the Magnéli nanoparticles was quantitatively evaluated under different atmospheres with synchrotron radiation-based X-ray photoelectron spectroscopy, highlighting oxidized surfaces with lower conductivity than the core. This finding sheds a new light on the charge transfer occuring in these materials.

EurJIC2019-2

E. Baktash, J. Capitolis, L. Tinat, C. Larquet, T. H. C. Chan Chang, J.-J. Gallet, F. Bournel, C. Sanchez, S. Carenco, D. Portehault. Chem. Eur. J. 2019, 25, 11114-20.

Ensemble versus Local Restructuring of Core-shell Nickel-Cobalt Nanoparticles upon Oxidation and Reduction Cycles

Bimetallic nanoparticles are widely studied, for example in catalysis. However, possible restructuring in the environment of use, such as segregation or alloying, may occur. Taken individually, state‐of‐the‐art analytical tools fail to give an overall picture of these transformations.

In collaboration with Cecile S. Bonifacio and Judith C. Yang from Pittsburg University, we studied nickel-cobalt nanoparticles exposed to reactive gases. Combination of an ensemble technique (NAP-XPS) and a local one (environmental TEM) was pivotal for describing the nanoparticles transformations.

ChemEurJ2018

S. Carenco, C. S. Bonifacio, J. C. Yang, Chem. - A Eur. J. 2018, 24, 12037-43.

Synthesis of Ce2O2S and Gd2(1– y)Ce2yO2S Nanoparticles and Reactivity from in Situ X-ray Absorption Spectroscopy and X-ray Photoelectron Spectroscopy

This article describes the synthesis of bimetallic oxysulftide nanoplatelets. They could be obtained over the whole (Gd,Ce) composition range with good control of size and cristallinity.

We observed that cerium-rich nanoparticles are less stable in air than Gd-rich nanoparticles. With in situ X-ray absorption and X-ray photoelectron spectroscopy, we could demonstrate that (i) all these nanoparticles actually exhibit surface sulfate, (ii) sulfate form as a consequence of exposure to water and/or oxygen, (iii) there is a threshold of 50% Ce above which the structure is not stable anymore in air, due to the formation of Ce(IV) species.

InorgChem2017-2

C. Larquet, A.-M. Nguyen, M. Ávila-Gutiérrez, L. Tinat, B. Lassalle-Kaiser, J.-J. Gallet, F. Bournel, A. Gauzzi, C. Sanchez, S. Carenco, Inorg. Chem. 2017, 22, 14227-14236

The Birth of Nickel Phosphides Catalysts: Monitoring Phosphorus Insertion into Nickel

Using in situ ambient-pressure X-ray photoelectron spectroscopy, the formation of nickel phosphide on the surface of a nickel foil was investigated, at temperatures like those employed to form nickel phosphide nanoparticles in colloidal route using tri-n-octylphosphine as a phsophorus source.

Our results demonstrate that even below 150 °C, significant phosphorus and carbon incorporation can occur during metal nanoparticles syntheses that employ TOP as stabilizing agent. These findings provide new insight on the surface chemistry of metal phosphide nanoparticles, increasingly employed in several fields of catalysis.

ChemCatChem2017

S. Carenco, Z. Liu, M. Salmeron, ChemCatChem 2017, 9, 2318–2323

In Situ Solid-Gas Reactivity of Nanoscaled Metal Borides from Molten Salt Synthesis

Our study about cobalt boride nanoparticles, led by David Portehault, uses Near-Ambient-Pressure XPS to monitor the behavior of this CO2 methanation catalyst.

We uncovered that the crystalline structure is not stable in reducing conditions and evolves to metallic cobalt and boron oxide. This surprising result was confirmed by NEXAFS measurements and additional characterizations.

InorgChem2017

G. Gouget, D. P. Debecker, A. Kim, G. Olivieri, J.-J. Gallet, F. Bournel, C. Thomas, O. Ersen, S. Moldovan, C. Sanchez, S. Carenco, D. Portehault. Inorg. Chem. 2017, 56, 9225–9234

Reviews papers:

Describing inorganic nanoparticles in the context of surface reactivity and catalysis

Surface and core of inorganic nanoparticles may undergo profound transformations in their environment of use. Accurate description is key to understand and control surface reactivity.

Through a selection of case studies, this feature article proposes a journey from surface science to nanoparticle design, while illustrating state-of-the-art spectroscopies that help provide a relevant description of inorganic nanoparticles in the context of surface reactivity.

ChemComm2018

S. Carenco, Chem. Commun. 2018, 54, 6719-6727

 

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